It is twenty years ago, and I am watching Tiffany, apple-faced and wholesome, holding a straight razor and standing in a bathtub filled with blood.

“Are you okay? Do we need to stop?”

Soaking wet in only a thin cotton shirt, she trembles. She seems entranced by the blood running down her arms and legs. “No, I’m fine,” she assures me, her eyes suddenly sparkling. “This is perfect.” Then, possessed by something dark and unexpected, Tiffany stares right at me, and slowly runs the straight razor over her tongue.

The blood is fake; the razor is a blunt-edged prop, but several of the film students packed into my apartment bathroom cry out in alarm. I nearly drop the Super-8 camera. Later, when I’m hand-cranking the film, thin as correction tape, through the dim viewer, I re-watch this moment over and over, and each time I shudder.

By day Tiffany is a polite and prudent bank teller, but for that one moment she is Lilith, terrifying and sublime, rising from a crimson lake to take her revenge on the sons of Adam. Somehow, the stage blood has evoked a metamorphosis.

And, somehow this is all connected to the Halloween re-release of The Exorcist in 1979. Now I am thirteen-years-old, sitting in an auditorium with hundreds of civilized adults, watching a girl around my age gleefully abuse herself with a crucifix, splattering her bed-sheets and smearing the blood across her mother’s face. I look at adult faces in the audience, frozen and impassive. How is this happening? How is this okay? Much later, I will wonder if the horror, violence and perversity in my screenplays are just echoes of that primal childhood trauma.

All my memories of Hollywood are soaked in stage blood. I mopped up bloody footprints between takes on Slumber Party Massacre III. I trashed the blood-speckled plastic that wrapped Laura Palmer’s corpse. I combed through a draft of Halloween: Resurrection finding synonyms for “stab.” I counted the number of beheadings in a draft of Conan The Barbarian and decided to limit myself to six. I accidentally spilled a pint on the floor of my brother-in-law’s Jeep so that for years afterwards, every time it rained, his car would bleed.

I have been paid to write around twenty-five screenplays and teleplays, and not one of them didn’t call for stage blood. This really shouldn’t surprise me.

Blood is a metaphor older than language, originating on the walls of caves. Blood evokes ritual sacrifice and the fragility of human flesh. Blood means madness, panic, and transformation. Blood is the puncture of order and the gushing of chaos.

It’s the flood from the elevator doors in The Shining. It’s the stain on the teeth in Jaws. It’s not so much the pig-bloodied prom dress, but the look in Carrie’s eyes. What blood means, what I want stage blood to mean, is terror in the sublime.

But usually, it doesn’t.

Instead of poetic or uncanny, the stage blood that bubbles up in my credited movies and television often turns out campy, unintentionally comic, and only mildly grotesque. Still, I keep a vial of it by my writing desk. For me, Halloween will always be about the feeling I got when Tiffany let blood spill out of her mouth and run down her chin, her lips curling into a ghastly little smile.